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Add -mno-shared to x86 assembler

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On ELF target, the assembler normally generates code which can go into a
shared library where non-weak symbols can be preempted.  The -mno-shared
option tells the assembler to generate code not for a shared library,
where non-weak symbols won't be preempted.  The resulting code is slightly
smaller.  This option mainly affects the handling of branch instructions.

gas/

	* config/tc-i386.c (no_shared): New.
	(OPTION_MNO_SHARED): Likewise.
	(elf_symbol_resolved_in_segment_p): Check no_shared.
	(md_longopts): Add mno-shared.
	(md_parse_option): Handle OPTION_MNO_SHARED.
	(md_show_usage): Add -mno-shared.
	* doc/c-i386.texi: Document -mno-shared.

gas/testsuite/

	* gas/i386/i386.exp: Run relax-4 and x86-64-relax-3.
	* gas/i386/relax-4.d: New file.
	* gas/i386/x86-64-relax-3.d: Likewise.
This commit is contained in:
H.J. Lu 2015-05-08 05:04:12 -07:00
parent 422349a385
commit 573cc2e57d
7 changed files with 110 additions and 0 deletions
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10
gas/ChangeLog
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@ -1,3 +1,13 @@
2015-05-08 H.J. Lu <hongjiu.lu@intel.com>
* config/tc-i386.c (no_shared): New.
(OPTION_MNO_SHARED): Likewise.
(elf_symbol_resolved_in_segment_p): Check no_shared.
(md_longopts): Add mno-shared.
(md_parse_option): Handle OPTION_MNO_SHARED.
(md_show_usage): Add -mno-shared.
* doc/c-i386.texi: Document -mno-shared.
2015-05-07 H.J. Lu <hongjiu.lu@intel.com>
* config/tc-i386.c (elf_symbol_resolved_in_segment_p): New.

17
gas/config/tc-i386.c
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@ -524,6 +524,11 @@ static enum x86_elf_abi x86_elf_abi = I386_ABI;
static int use_big_obj = 0;
#endif
#if defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF)
/* 1 if not generating code for a shared library. */
static int no_shared = 0;
#endif
/* 1 for intel syntax,
0 if att syntax. */
static int intel_syntax = 0;
@ -8785,6 +8790,10 @@ elf_symbol_resolved_in_segment_p (symbolS *fr_symbol)
/* Symbol may be weak or local. */
return !S_IS_WEAK (fr_symbol);
/* Non-weak symbols won't be preempted. */
if (no_shared)
return 1;
/* Global symbols with default visibility in a shared library may be
preempted by another definition. */
return ELF_ST_VISIBILITY (S_GET_OTHER (fr_symbol)) != STV_DEFAULT;
@ -9484,6 +9493,7 @@ const char *md_shortopts = "qn";
#define OPTION_MBIG_OBJ (OPTION_MD_BASE + 18)
#define OPTION_OMIT_LOCK_PREFIX (OPTION_MD_BASE + 19)
#define OPTION_MEVEXRCIG (OPTION_MD_BASE + 20)
#define OPTION_MNO_SHARED (OPTION_MD_BASE + 21)
struct option md_longopts[] =
{
@ -9494,6 +9504,7 @@ struct option md_longopts[] =
#endif
#if defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF)
{"x32", no_argument, NULL, OPTION_X32},
{"mno-shared", no_argument, NULL, OPTION_MNO_SHARED},
#endif
{"divide", no_argument, NULL, OPTION_DIVIDE},
{"march", required_argument, NULL, OPTION_MARCH},
@ -9554,6 +9565,10 @@ md_parse_option (int c, char *arg)
/* -s: On i386 Solaris, this tells the native assembler to use
.stab instead of .stab.excl. We always use .stab anyhow. */
break;
case OPTION_MNO_SHARED:
no_shared = 1;
break;
#endif
#if (defined (OBJ_ELF) || defined (OBJ_MAYBE_ELF) \
|| defined (TE_PE) || defined (TE_PEP) || defined (OBJ_MACH_O))
@ -9980,6 +9995,8 @@ md_show_usage (FILE *stream)
-mold-gcc support old (<= 2.8.1) versions of gcc\n"));
fprintf (stream, _("\
-madd-bnd-prefix add BND prefix for all valid branches\n"));
fprintf (stream, _("\
-mno-shared enable branch optimization for non shared code\n"));
# if defined (TE_PE) || defined (TE_PEP)
fprintf (stream, _("\
-mbig-obj generate big object files\n"));

10
gas/doc/c-i386.texi
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@ -297,6 +297,16 @@ The @code{.att_syntax} and @code{.intel_syntax} directives will take precedent.
This option forces the assembler to add BND prefix to all branches, even
if such prefix was not explicitly specified in the source code.
@cindex @samp{-mno-shared} option, i386
@cindex @samp{-mno-shared} option, x86-64
@item -mno-shared
On ELF target, the assembler normally generates code which can go into a
shared library where non-weak symbols can be preempted. The
@samp{-mno-shared} option tells the assembler to generate code not for
a shared library, where non-weak symbols won't be preempted. The
resulting code is slightly smaller. This option mainly affects the
handling of branch instructions.
@cindex @samp{-mbig-obj} option, x86-64
@item -mbig-obj
On x86-64 PE/COFF target this option forces the use of big object file

6
gas/testsuite/ChangeLog
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@ -1,3 +1,9 @@
2015-05-08 H.J. Lu <hongjiu.lu@intel.com>
* gas/i386/i386.exp: Run relax-4 and x86-64-relax-3.
* gas/i386/relax-4.d: New file.
* gas/i386/x86-64-relax-3.d: Likewise.
2015-05-07 H.J. Lu <hongjiu.lu@intel.com>
* gas/i386/i386.exp: Run relax-3 and x86-64-relax-2.

2
gas/testsuite/gas/i386/i386.exp
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@ -396,6 +396,7 @@ if [expr ([istarget "i*86-*-*"] || [istarget "x86_64-*-*"]) && [gas_32_check]]
run_dump_test "note"
run_dump_test "relax-3"
run_dump_test "relax-4"
}
# This is a PE specific test.
@ -752,6 +753,7 @@ if [expr ([istarget "i*86-*-*"] || [istarget "x86_64-*-*"]) && [gas_64_check]] t
run_list_test "x86-64-size-inval-1" "-al"
run_dump_test "x86-64-relax-2"
run_dump_test "x86-64-relax-3"
}
set ASFLAGS "$old_ASFLAGS"

32
gas/testsuite/gas/i386/relax-4.d Normal file
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@ -0,0 +1,32 @@
#source: relax-3.s
#as: -mno-shared
#objdump: -dwr
.*: +file format .*
Disassembly of section .text:
0+ <foo>:
[ ]*[a-f0-9]+: eb 1c jmp 1e <local>
[ ]*[a-f0-9]+: eb 16 jmp 1a <hidden_def>
[ ]*[a-f0-9]+: eb 16 jmp 1c <global_def>
[ ]*[a-f0-9]+: e9 fc ff ff ff jmp 7 <foo\+0x7> 7: (R_386_PC)?(DISP)?32 weak_def
[ ]*[a-f0-9]+: e9 fc ff ff ff jmp c <foo\+0xc> c: (R_386_PC)?(DISP)?32 weak_hidden_undef
[ ]*[a-f0-9]+: e9 fc ff ff ff jmp 11 <foo\+0x11> 11: (R_386_PC)?(DISP)?32 weak_hidden_def
[ ]*[a-f0-9]+: e9 fc ff ff ff jmp 16 <foo\+0x16> 16: (R_386_PC)?(DISP)?32 hidden_undef
0+1a <hidden_def>:
[ ]*[a-f0-9]+: c3 ret
0+1b <weak_hidden_def>:
[ ]*[a-f0-9]+: c3 ret
0+1c <global_def>:
[ ]*[a-f0-9]+: c3 ret
0+1d <weak_def>:
[ ]*[a-f0-9]+: c3 ret
0+1e <local>:
[ ]*[a-f0-9]+: c3 ret
#pass

33
gas/testsuite/gas/i386/x86-64-relax-3.d Normal file
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@ -0,0 +1,33 @@
#source: relax-3.s
#as: -mno-shared
#objdump: -dwr
.*: +file format .*
Disassembly of section .text:
0+ <foo>:
[ ]*[a-f0-9]+: eb 1c jmp 1e <local>
[ ]*[a-f0-9]+: eb 16 jmp 1a <hidden_def>
[ ]*[a-f0-9]+: eb 16 jmp 1c <global_def>
[ ]*[a-f0-9]+: e9 00 00 00 00 jmpq b <foo\+0xb> 7: R_X86_64_PC32 weak_def-0x4
[ ]*[a-f0-9]+: e9 00 00 00 00 jmpq 10 <foo\+0x10> c: R_X86_64_PC32 weak_hidden_undef-0x4
[ ]*[a-f0-9]+: e9 00 00 00 00 jmpq 15 <foo\+0x15> 11: R_X86_64_PC32 weak_hidden_def-0x4
[ ]*[a-f0-9]+: e9 00 00 00 00 jmpq 1a <hidden_def> 16: R_X86_64_PC32 hidden_undef-0x4
0+1a <hidden_def>:
[ ]*[a-f0-9]+: c3 retq
0+1b <weak_hidden_def>:
[ ]*[a-f0-9]+: c3 retq
0+1c <global_def>:
[ ]*[a-f0-9]+: c3 retq
0+1d <weak_def>:
[ ]*[a-f0-9]+: c3 retq
0+1e <local>:
[ ]*[a-f0-9]+: c3 retq
#pass